Colour accuracy is a critical performance specification of a printing device. In many applications very high accuracy (up to an accuracy of ΔE≦0.5) is required for a number of reasons. ΔE is a measure of the colour difference between two colours, which is perceivable to the human eye. A ΔE value of one is the smallest colour difference perceivable to the human eye. Company logos are an example where a high degree of precision is required. Another example is when colour matching is required between a few printing devices, for example when digital prints are used to complete a run of a non-digital printing device, or when several prints are presented together. Consumer product packaging are often comprised of a plurality of prints originating from different sources. In such applications, colour accuracy between the different prints is crucial. One of the most demanding applications requiring high accuracy (possibly the highest) is when a label is required to match the colour of a product—this is the case when printing labels for ink cans, wall paint cans, hair dye, etc.
Currently several methods are used to achieve the requirements of high colour accuracy. The most common method is to use the Pantone colour conversion tables. These are colour conversions that were built specifically to match the Pantone swatch books. However, in some cases, due to a number of reasons such as press variability, ink variability, different type of substrates, etc., the first printed run of the colour, using the given values of the conversion, will produce a result that can be improved and needs to be improved for the given application. This improvement is usually done by an iterative procedure using an external measuring device or by a visual match to get closer to the desired target, increasing the setup time for each job. In cases where the desired colour is not part of the Pantone swatch book the regular conversions that are used produce even less accurate results.
Another solution is to use special inks with the exact colour of the desired target colour. This can be an acceptable solution where only very few colours are printed and where very long runs of the press are performed using the specific ink. This solution requires that an additional ink be supported and maintained in the press. In applications where several specific colours are required for a particular job, or where short runs of the press each with a different colour are required, this solution is not acceptable.